This invention relates to magnetic recording and more particularly, to a driver circuit for producing bi-directional write current through a magnetic head.
In magnetic recording, the magnetic write head is commonly driven with current in one direction or the other through the head winding to produce bi-directional recording. In magnetic tape systems, it has been common practice to use a write head with a center tap which was connected to reference potential. This produced voltage excursions on both sides of the write head winding which were equal and opposite. The equal and opposite voltage excursions minimized the feed through of transients to the read head circuit. Because the voltage excursions were equal and opposite, the transients which are capacitively coupled to the read circuit are equal and opposite and tend to cancel.
Recently, thin film resistives have been developed for magnetic recording, particularly magnetic tape recording. These heads are produced by a photoresist process. For several reasons, it is not practical to provide a center tap on the head. For one reason, this requires a manual step which is not compatible with the high speed photoresist deposition of the heads.
"PREDRIVER FOR `H` CONFIGURED WRITE DRIVER FOR MAGNETIC RECORDING", by J. A. Bailey, R. G. Black, Jr., and J. Lewkowicz, IBM TECHNICAL DISCLOSURE BULLETIN, Vol. 23, No. 11, Nov. 1981, shows a write driver for a thin film magnetic write head. The driver transistors are connected in an H-configuration with two driver transistors being turned on to produce current through the head in one direction, and the other being turned on to provide current through the head in the other direction. In such a circuit, the voltage excursions on the two sides of the head are not equal and opposite. Because of this, transients are capacitively coupled to the read circuitry.
It is an object of the present invention to provide a write driver circuit for a thin film magnetic head which has an artificial center tap and which reduces feed through of transients to the read circuit.